Alpha = an alphabetic character (a - z)
16.5.3 HWRPB: Console Terminal Block Portion
The console terminal block (CTB) is the primary data structure that indicates
which device is the current console terminal and describes its characteristics. The
CTB is quadword-aligned; its starting address is an offset from the beginning of
the HWRPB; the offset pointer is saved at HWRPB[B8].
During console initialization, the console:
• Selects a device as the console device
• Builds a CTB to identify the console device
• Initializes the console terminal
• Records the default state in the CTB
• Places the offset from the beginning of the HWRPB to the CTB at
HWRPB[B8]
Only one CTB can be built at a time; only one console device can be active at a
time. The console does not support multiple console devices and does not allow
the system software to switch the console terminal dynamically. The console
terminal can be switched only before the system software is booted. The operator
issues the SET CONSOLE TERMINAL command to do so.
The CTB consists of two parts:
• A common formatted segment
• A device-dependent segment, containing data that varies according to the
console device. The DEC 3000 AXP supports these console types:
Terminal connected to the serial communication controller
Graphics device
Network device
Figure 29 shows the general format of a CTB.
The next table lists the components of a CTB.
Console 16–43
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